Electron microscopes are used in neuroscience, cell biology, microtechnologies, material science, and so forth to collect large quantities of data. Commonly, an amount of time required to collect imagery using an electron microscope can be a hindrance. For example, various efforts to image a mouse brain have conventionally taken several months of dedicated scanning electron microscope imaging time for every cubic millimeter of tissue. Moreover, it may be desirable to collect terapixels of imagery, with resolution of approximately 10 nm2 per pixel, orders of magnitude more quickly than conventional scanning electron microscopes can achieve. Such capability can elucidate the inner workings of complex biological systems, to enable new inspection methods for microcircuit process controls, and the like.
Conventional scanning electron microscopes acquire an image pixel-by-pixel by raster scanning a small electron beam across a sample and recording a signal with a single detector. While many optical systems commonly use an array of photodetectors, electron microscopy approaches generally employ a single detector (or small number of detectors on the order of ten detectors) due to operation of such detector (e.g., collecting nearby electrons). Further, an amount of time to acquire an image is typically limited by Nyquist conditions and signal to noise ratios (SNRs). For instance, the Nyquist conditions can involve every pixel being visited by an electron beam, one at a time. Further, a length of time that the electron beam dwells on a given pixel can be proportional to a desired SNR.
Various conventional scanning electron microscope designs can support developing an image of an area of a sample by sequentially measuring brightness values (e.g., determined by secondary or back-scattered electron detectors) of each pixel of the image. Conventional scanning electron microscopes typically include an electron source that generates electrons (e.g., field emission electron source). Moreover, conventional scanning electron microscopes commonly include an acceleration component that drives electrons away from the electron source and send the electrons down a column of the scanning electron microscope. The electrons can proceed down the column and pass through various lenses, such as a condenser lens, which can shape the distribution of electrons to provide desired geometric properties, and an objective lens, which focuses the beam on the sample surface. The lenses of the scanning electron microscope can be electromagnetic lenses that alter electrical properties of the electrons. Moreover, differing designs of conventional scanning electron microscopes can include disparate electromagnetic lenses. Conventional scanning electron microscopes also commonly include an aperture and a scanning coil. The electrons can impinge upon the aperture to reduce a broad beam of electrons down to a single narrow beam. For instance, the narrow beam can have a diameter on the order of a few nanometers or less than a nanometer. The scanning coils can be a set of electromagnetic components that can direct the beam coming from the aperture to a specified location on a sample, thereby allowing one pixel to be measured at a time. The beam can interact with the sample and a response can be measured at a detector. The foregoing can be repeated for each pixel to be scanned when generating the image of the sample.